Pole barn ceiling/roof insulation options?

[DENALIAKITAS]

I will be having a 30x40 pole barn/building constructed for a work shop. I plan to use closed cell spray foam for the exterior walls but i am unsure how the best way to go about sealing/insulating the ceiling and/or roof. Should i spray foam the underside of the roof as well or would it be better to put a ceiling/liner on the bottom of the trusses then blow in some cellulose or artic cat fiberglass on top of that? If i go the latter route would there be any issues with condensation forming on the bottom of the roof tin? Thanks for your input.

 

[Jbullfrog]

You have to use a vapor barrier between the ceiling steel and the blown in insulation. This will keep the heat and or cold contained within and the roof steel will be what ever the temperature is on the otherside of it.

 

[crewguy]

The guys down here use 6" batt insulation and either chicken wire or plastic to cover the batts. However we use the metal trusses spaced @ 12'.

 

[K'ledgeBldr]

Spraying the whole thing would be the best-
No vapor barrier, no air gap, chicken wire, battens, baffles, etc., etc., etc.

 

[cyamaha2007]

if i could go back id spray it all. More money but far better.

 

[PeterT]

I used unfaced R30 batts, laying directly on the metal panels (20'x3' ceiling panels) in my pole barn, its about 50x95.
I haven't had any moisture issues and it keeps the barn comfortable.

Home Depot had the pink stuff on sale for about $10 a roll.

 

[93L#3008]

anyone paint their rafters black and spray foam against the metal? I will have 16'scissor trusses and have seen this in restaurants and commercial buildings. Lights would hang from trusses. Might be an alternative to expense of metal ceiling and time to install.

 

[Drinkin-N-Thinkin]

Insulating a metal building is obviously a widely debated topic with many different perspectives and techniques (I am building a 36x54 workshop and I'm at this stage now). I plan on spraying as well, but here's is what I learned from my research:
1) When spraying the walls, at least 1/2 the R value of the wall should be closed cell foam; this is to put the condensation point inside the foam. It's not cheap--but I'll just do a 1 inch layer at a time as I can affort it. If you're only planning on spraying an inch with nothing else this won't matter, but if you are planning on adding more insulation and enclosing the wall keep this in mind.
2) For the ceiling, you can spray 1 inch of foam on the top of the ceiling (attic side) as an air barrier; put some poly up on the inside of the ceiling (warm side--since you are only using 1 inch) and blow on top of that. Make sure you don't block the eave vents to maintain adequite ventilation.
3) Insure you have PLENTY of ventilation around the parimeter at the eaves and decide if you want to vent naturally with a ridge vent or powervent. I increased my eaves to 24 inches all the way around and very glad I did it. I chose two 10 inch ridge vents.
4) I am considering not spraying the roof part (or only doing the center, staying off the perlins) because after a while (if you have the standard raised rib panel with the screw at the top of the rib) I think those rubber washers that seal the fastener will cook out and become a potential leak point. If the roof is foamed underneath, there won't be anywhere for the water to go causing a potential for the metal roof to rust or trusses to rot and possibly void the warranty. That's my situation. If you haven't built yet and still want to spray the roof, I would put plywood on top of the perlins then tar paper (or some other barrier) then the metal and you can foam underneith the plywood. I have been told by my manufacturer just insulating the ceiling and leaving the roof should be fine (I explained this entire plan to them).
5) Don't forget the floor--concrete is very porous. Minimum: poly under the concrete, possibly seal the surface after that. Not sure if you are thinking of it or how cold it is there for you, but if you can, insulate the bottom and sides of the floor with 2" foam and run PEX tube in it now so later you can heat with radiant. If you are doing a frost wall, make sure the slab floats.

 

[Dave Maxwell]

I am Puting 2 inch foamboard 2 foot down verticaly. My slab isn't floating though. It has metal out riggers on each post that will be in the concrete. Is that ok

 

[Drinkin-N-Thinkin]

I am Puting 2 inch foamboard 2 foot down verticaly. My slab isn't floating though. It has metal out riggers on each post that will be in the concrete. Is that ok

The reason for a floating slab is so the weight of the building isn't pushing down on the perimeter of a flat slab which will create a crack in the middle. If you have metal posts that go through the concrete say 4 feet down, the weight of the building will transfer the building weight to the solid ground below. A good precaution would be to make sure there is some leaway between the metal outriggers and the slab so both are free to "seek their own level" as the ground shifts. You can use foam or the expansion strips.

 

[maddy]

Spray foam insulation will be better choice for roof and ceiling as you can get the desirable results in quick time. most of the time fiberglass material doesn't provide good strength to walls and that's why people have to look on spray method.

 

[mx842]

If you don't mind seeing the truss system then spray the whole roof solid from the roof line to the peak, no ventilation. You can either install blocking in between the truss of just put a bit of batt insulation in the hole and cover it up with foam. Once the foam sets spray it white and forget about it. This system works great if you have several clear panels installed in the roof to let in additional free light.

 

[yotehuntersd]

I built a 24x28 garage last year. Stick built 16" oc side walls with purlins outside that and 24"oc rafters with purlins outside that. Screwed steel straight to the purlins on the walls and ceiling. Had it spray foamed 2" on sidewalls and ceiling straight on the metal. They sprayed over 3" on most of it. There is effectively 2" of foam surrounding every inch of concrete and sidewall and roof. Two of my sidewalls are 54" icf's. I have 1 overhead door its 9'x16'x2" thick
Things I learned and or would do differently.
1. I put 2" foam under my slab wish I would have put 4".
2. The spray foam will bow/buckle your steel at every purlin. Visible in decent sunlight. I am ok with it but picky people might not be. It does make the building solid as a rock once its sprayed.
3. I live in S Dakota and I have 10' ceilings, I think I should have sheeted the ceiling and foamed the attic side of the ceiling for the seal then blew in R-? however much more to insulate.
Overall I heated it to 45 deg with electric in floor heat for $150 last winter - also we had the warmest winter on record too.

 

[Cougar]

I used unfaced R30 batts, laying directly on the metal panels (20'x3' ceiling panels) in my pole barn, its about 50x95.
I haven't had any moisture issues and it keeps the barn comfortable.

Home Depot had the pink stuff on sale for about $10 a roll.

How far are your trusses spaced.
Did you add anything to fasten the panels to.

 

[Dave Maxwell]

Here is a pic of the outriggers I mentioned that tie the building to the post

 

[Dave Maxwell]

Bobbie. Is there I pic with your post. My email showed there was a link. But post doesn't shoe one on my phone

 

[NUTTSGT]

Bobbie. Is there I pic with your post. My email showed there was a link. But post doesn't shoe one on my phone

Dave, that user is a possible spammer. Every post they have made has that link but nothing shows below it. They have made 7 posts in 6 minutes. I've alerted one of the mods to check them out. I hate to be that way but we don't need crappy spammers here.

 

[Dave Maxwell]

Thanks

 

[Drinkin-N-Thinkin]

Here is a pic of the outriggers I mentioned that tie the building to the post

Hmm...I was imagining the "outriggers" were actually the posts, but in metal. I'm not sure what purpose those were intended to serve or problem they are to prevent, but they would certainly tie the building to the posts preventing the slab from floating as the ground heaves. If it were me, I wouldn't use them, but would make sure my building is on a consistant footing. Are they only on the side of the building that is higher (I'm assuming a sloping lot)?

 

[cyamaha2007]

^^^ I was told to be sure the slab can float in a pole barn. I wrapped the post with foam so the concrete can move and not push on the building.

 

[Dave Maxwell]

They are all the way around the building
. County code requires the post to be tied in from my understanding

 

[cyamaha2007]

The problem i see is when the slab wants to move it will and it will likely crack or pull on your brackets. If your slab will have a footer, the footer could be tied to the post. Its just not common to have slab footer with a pole barn.

 

[Dave Maxwell]

The post are on metal stands and then cemented in. Think they said three or four feet down. I know I hit some concrete while digging for perimeter foam. Getting worried about floor now

 

[Stickbait]

Trying to find a simple answer, lots of looking, apologize if in wrong place, roof insulation, 30x40x16.

Roof layers are: metal, synthetic underlayment, 7/16s osb, 2x8 trusses and purlins 24" oc.

So with those layers I can use any type of insulating options correct? Looking at fiberglass rolls unbatted, so will need to cover with plastic correct? TYIA.